Activated carbon monolith catalyst, methods for making same, and uses thereof

ABSTRACT

An activated carbon monolith catalyst comprising a finished self-supporting activated carbon monolith having at least one passage therethrough, and comprising a supporting matrix and substantially discontinuous activated carbon particles dispersed throughout the supporting matrix and at least one catalyst precursor on the finished self-supporting activated carbon monolith. A method for making, and a method for use, of such an activated carbon monolith catalyst in catalytic chemical reactions are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/102,452, filed Apr. 8, 2005, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to catalytic structures, methodsfor making same, and uses thereof. In particular, this invention relatesto activated carbon monolith catalysts and methods for making and usingthem.

BACKGROUND OF THE INVENTION

Carbon catalysts play an important role in various chemical processesfrom industrial to pharmaceutical settings. Carbon catalysts enablechemical reactions to occur much faster, or at lower temperatures.because of changes that they induce in the reactants. Carbon catalystsmay lower the energy of the transition state of chemical reactions, thuslowering the activation energy. Therefore, molecules that would not havehad the energy to react, or that have such low energies that it islikely that they would take a long time to do so, are able to react inthe presence of a carbon catalyst by reducing the energy required forthe reaction to occur. Not only do carbon catalysts increase the rate ofreaction, but they may also drive a reaction towards the desiredproduct.

Typically, catalysts are applied to a substrate before introduction to achemical process. Desirably, the substrate holds the catalyst whilepresenting the catalyst to reactants in the chemical process.Conventional catalyst substrates, or supports, include carbon or ceramicgranules arranged in a bed, and ceramic monoliths.

Traditionally, carbons utilized as catalyst supports are either granulesor powders. In a perfect world, carbons used for catalyst supports wouldbe chosen only for their activity and selectivity. The more commonfeatures that are important factors in determining activity andselectivity are surface area, pore volume, pore size, ash content,friability, availability, and/or other elements contained in the carbonmatrix. The foregoing are not the only desirable features; rather, theyare ones that are known to be obtainable within the art.

Conventionally, carbon catalyst supports are chosen more for propertiesthat meet parameters of the chemical process, than for features thatwould make purely the best catalyst, for highest activity andselectivity. While a particular carbon substrate might have the bestfeatures for activity and selectivity, it may not be the best choiceconsidering the chemical process parameters. For example, carbongranules suffer from attrition making exact pressure drop determinationsdifficult, and they scale up poorly in chemical processes. When chemicalreactants trickle through a bed of granular carbon catalyst, thecatalyst must be as attrition resistant as possible, less the bedcollapse and flow cease or the catalyst metals be lost. Attrition is aparticularly aggravating issue, because it alters the physicalparameters of the chemical process as it proceeds, and causes financialloss, particularly when the catalyst is a precious metal. For thisreason, carbons of choice are typically nutshell carbons, which aredurable, but which have very small pores that can harshly limit activityand selectivity. When a powder carbon catalyst is stirred violently in abatch reactor with chemical reactants, the carbon catalyst must benon-friable to some degree to allow it to be economically separated fromthe reaction at termination in order to prevent loss of the catalyst.Thus, perhaps one must exclude carbons with better catalytic properties,but which are too friable.

Ceramic catalytic monoliths have been used in the art for advantagesthey provide over fixed bed supports, such as predictable pressure dropthrough the catalyst bed, scalability based on a model that predictsperformance through incremental increases in volume of catalyst withrespect to the same reactant volume flow, separation of the catalystsfrom the reaction and from the product stream, practical continuousoperation and ease of replacement of the catalyst, and layering of thecatalyst or the catalysts either on the monoliths' wall depth or walllength, or both. The low pressure drop of catalytic monoliths' allowsthem to operate at higher gas and liquid velocities. These highervelocities of gas and liquids promote high mass transfer and mixing.

Catalytic monolith development has been an ongoing process in an effortto enhance catalytic activity, catalytic selectivity, and catalyst life.Although monoliths have advantages over fixed bed supports, there arestill problems associated with traditional ceramic monoliths. Exposureof the catalytic metal in the catalytic monolith to the reactants isnecessary to achieve good reaction rates, but efforts to enhanceexposure of the catalytic metal often have been at odds with efforts toenhance adhesion of the metal to the monolith substrate. Thus, catalyticceramic monoliths have fallen short of providing optimal catalyticselectivity and activity.

As seen below, ceramic carbon catalyst monoliths developed to date, onone hand may provide good selectivity and activity, but on the otherhand may not be suitable for process parameters such as durability andinertness. Conversely, ceramic carbon catalyst monoliths suitable forsuch process parameters may have diminished selectivity and activity.Thus, it would be ideal to take a carbon with the best features for acatalyst based on its activity and selectivity, and then form a carbonmonolith catalyst to flit the process parameters of choice.

There have been efforts to form a carbon support that would have some ofthe features of a ceramic monolith catalyst. These efforts fall intothree general classes: gluing or binding of carbon granules or powder toform larger structures, coating ceramic monoliths with an organiccompound such as sugars or liquid polymer plastics, followed bycarbonization of the organic compound on the ceramic monolith, andformation of a structure from an organic material, such as a plastic ornylon, followed by carbonization of the structure.

The binding of carbons gives some degree of choice of carbon precursor,but the result is a carbon support with the binder as a new element.These binders can vary from organic glues to pitches. In most cases, thebinders are susceptible to attack by the reaction media in application.Some cause side reactions, or poison the catalyst. Furthermore, theresult is a random binding of granules, or the creation of a newgranule—a chopped extrudate of powdered carbon and binder. In eithercase, the parameters of flow are not predictable by simple,understandable models. Although the carbons selected have generally beenin use as unbound catalyst supports, and unbound activity andselectivity information on the carbon can sometimes be used, still thebinder is not inert, and therefore binder influence is always an issue.

Carbonization of an organic material forms a support with little hope ofprior carbon activity or selectivity information. Because the carbon isformed each time the support is prepared, and is limited to thoseprecursor and organic materials that can be coated or formed andcarbonized, commercially available carbons, known in the art to produceexcellent catalyst, are excluded from consideration. Furthermore, thecarbons normally used in preparation of catalyst supports are preparedfrom naturally occurring materials such as wood, peat, nutshell, andcoal, and not from refined or organic chemicals. Carbon produced fromnaturally occurring material is known to retain some of the beneficialstructural characteristics as well chemical nature of the precursormaterial. These characteristics are known to be important to the finalactivity and selectivity of the catalyst. While carbonization may be away of producing a carbon coating or structure, it extends marginallythe catalyst art, and does not produce a catalyst utilizing the knowncarbon methods of choice in the art.

Thus, there is a need in the art for a carbon monolith catalyst, and aprocess for making the same, having attrition resistance, predictablepressure drop, high selectivity, high activity, and scalability forcommercial economy and efficiency. More particularly, there is a need inthe art to provide an activated carbon monolith catalyst which allowsthe manufacture of the catalyst of choice to fit the process parameters,while increasing the utility of the catalyst with predictable pressuredrop through the catalyst bed, scalability based on a model thatpredicts performance through incremental increases in volume of catalystwith respect to the same reactant volume flow, separation of thecatalysts from the reaction and from the product stream, practicalcontinuous operation and ease of replacement of the catalyst, andlayering of the catalyst or the catalysts either on the monolith's walldepth or wall length, or both, and while providing high selectivity andactivity.

SUMMARY OF THE INVENTION

Objects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention. Unless otherwise defined, alltechnical and scientific terms and abbreviations used herein have thesame meaning as commonly understood by one of ordinary skill in the artto which this invention pertains. Although methods and compositionssimilar or equivalent to those described herein can be used in thepractice of the present invention, suitable methods and compositions aredescribed without intending that any such methods and compositions limitthe invention herein.

The present invention addresses the above-described need by providing anactivated carbon monolith catalyst comprising a finished self-supportingactivated carbon monolith having at least one passage therethrough, andcomprising a supporting matrix and substantially discontinuous activatedcarbon particles dispersed throughout the supporting matrix, and atleast one catalyst precursor supported on the finished self-supportingactivated carbon monolith. The supporting matrix holds the activatedcarbon particles in a monolithic form. In preferred embodiments, thesupporting matrix comprises a ceramic or another substantially inertmaterial such as carbon.

The activated carbon monolith catalyst of this invention is not limitedto use of precursor materials that must be carbonized to form a carboncatalyst support. It can include any activated carbon particles from anysource. Thus, the activated carbon monolith catalyst of this inventioncan be made with activated carbon particles chosen for their superioractivity and selectivity for a given application. The activated carbonmonolith catalyst can then be expected to have a predictable activityand selectivity based on the knowledge available regarding theparticular activated carbon particles used. In addition, the activatedcarbon particles in the activated carbon monolith catalyst of thisinvention are dispersed throughout the structure of the catalyst, givingdepth to the catalyst activity and selectivity. The activated carbonparticles are bound by a supporting matrix, which desirably is an inertbinder and is not susceptible to attack by reaction media. Furthermore,the activated carbon monolith catalyst of this invention exhibits thedesirable features of a ceramic monolith, while also presenting theadvantage of a choice of a wide variety of particulate carbonsubstrates. Such desirable features include ease of separation of thecatalyst from a product in a chemical reaction, and predictable fluidflow, among others. Because the activated carbon particles are fixed ina monolithic form, regions of the monolith, in particular embodiments,can include different catalysts as desired. Such regions would notmigrate in monolithic form as they would with loose activated carbonparticles.

Accordingly, with the activated carbon monolith catalyst of thisinvention, the catalyst can be chosen based on its superior activity andselectivity, while pressure drop through the monolith is predictable,processes using the activated carbon monolith catalyst are scalablebased on a model that predicts performance through incremental increasesin volume of catalyst with respect to the same volume flow, and thecatalyst is separable from the reaction and product streams. Theactivated carbon monolith catalyst is useful in continuous operationswhich were formerly practical only in batch processes; the activatedcarbon monolith catalyst is easy to replace, and the catalyst precursorcan be layered either on the carbon monolith catalyst wall depth or walllength, or both. The activated carbon monolith catalyst of thisinvention can be used in continuous processes because a process streamcan flow through it. Due to the low pressure drop through the activatedcarbon monolith catalyst of this invention, continuous processes canoperate at high velocities.

In another embodiment of the present invention, a method for making anactivated carbon monolith catalyst is provided comprising providing afinished self-supporting activated carbon monolith having at least onepassage therethrough and comprising a supporting matrix andsubstantially discontinuous activated carbon particles dispersedthroughout the supporting matrix and applying at least one catalystprecursor to said finished extruded activated carbon monolith.

In another embodiment of the present invention, a method for catalyticchemical reaction is provided comprising contacting at least onereactant with an activated carbon monolith catalyst comprising (a) afinished self-supporting extruded activated carbon monolith having atleast one passage therethrough and comprising a supporting matrix andsubstantially discontinuous activated carbon particles dispersedthroughout the supporting matrix, and (b) at least one catalystprecursor on said finished extruded activated carbon monolith.

Other objects, features, and advantages of this invention will becomeapparent from the following detailed description of embodiments,drawings, and claims.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of an activated carbon monolith catalystmade in accordance with an embodiment of the invention.

FIG. 2 is a partial side elevation of an activated carbon monolithcatalyst of FIG. 1 with a portion of the skin removed to illustrate theflow of fluid through the honeycomb passages of the monolith.

In describing the proffered embodiment of the invention, which isillustrated in the drawings, specific terminology will be resorted tofor the sake of clarity. However, it is not intended that the inventionbe limited to the specific terms so selected, and it is to be understoodthat each specific term includes all technical equivalents which operatein a similar manner to accomplish a similar purpose.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference now will be made in detail to the presently profferedembodiments of the invention, one or more examples of which areillustrated in the accompanying drawings. Each example is provided byway of explanation of embodiments of the invention, not limitation ofthe invention. In fact, it will be apparent to those skilled in the artthat various modifications and variations can be made in the presentinvention without departing from the spirit or scope of the invention.For instance, features illustrated or described as part of oneembodiment, can be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention cover suchmodifications and variations within the scope of the appended claims andtheir equivalents.

As summarized above, this invention encompasses an activated carbonmonolith catalyst comprising a finished self-supporting activated carbonmonolith having at least one passage therethrough, and comprising asupporting matrix and substantially discontinuous activated carbonparticles dispersed throughout the supporting matrix, and at least onecatalyst precursor on the finished self-supporting activated carbonmonolith. A method for making an activated carbon monolith catalyst, andapplication of the activated carbon monolith catalyst in chemicalprocesses, are also disclosed. Embodiments of this invention aredescribed below, beginning with the structure and components of theactivated carbon monolith catalyst, followed by methods of making andusing the activated carbon monolith catalyst.

Carbon Monolith Catalyst Structure

As used herein, the term “activated carbon monolith catalyst” refers toa combination of an activated carbon monolith substrate and at least onecatalyst precursor. The term “catalyst” means a material that is presentin a reaction, adjusts the activation energy of the reaction andprovides some reaction selectivity, but is not consumed in the reaction.The term “catalyst precursor” means a material that is capable ofcreating a catalytically active site on a substrate material. A catalystprecursor may or may not undergo a change in becoming catalyticallyactive.

Suitable catalyst precursors are selected from precious metal, basemetal, or a combination thereof. Non-limiting examples of preciousmetals include, but are not limited to, palladium, platinum, rhodium,ruthenium, iridium, osmium, silver, and gold. The precious metal mayalso be reduced precious metal, precious metal oxide, precious metalsulfide, precious metal with modifiers, or a combination thereof.Non-limiting examples of modifiers include, but are not limited to,potassium, calcium, magnesium, sodium hydrated oxides, and sodiumhydroxides. Non-limiting examples of base metal include, but are notlimited to, zinc, nickel, copper, manganese, iron, chromium, vanadium,molybdenum, and combinations thereof. Base metal may also be present asoxides, hydrated oxides, carbonates, sulfides, or a combination thereof.An illustrative example of the combination of catalyst precursors may bea solution of palladium chloride and sodium carbonate, to be combinedwith an activated carbon monolith to form an activated carbon monolithcatalyst.

FIG. 1 illustrates an activated carbon monolith catalyst 10 madeaccording to an embodiment of the present invention. The activatedcarbon monolith catalyst 10 comprises a finished self-supportingactivated carbon monolith and at least one catalyst precursor applied tothe monolith. As used herein, the phrase “finished self-supportingactivated carbon monolith” refers to a solid-phase material comprisingactivated carbon without any catalyst precursor yet added to themonolith. The activated carbon monolith catalyst 10 shown in FIG. 1comprises an activated carbon monolith having a honeycomb shape andcomprising activated carbon particles, ceramic forming material, fluxmaterial, and water, to which at least one catalyst precursor has beenapplied. The activated carbon monolith catalyst has a plurality ofpassages 12 extending through the monolith from a frontal end 14 to arearward end 16. The passages 12 are substantially square in crosssection, linear along their length, and formed by surrounding walls 18,however, the passages can have other cross-sectional shapes such asrectangular, round, triangular, hexagonal, oval elliptical, and thelike. The passages 12 are encased by an outer skin 20 of the monolith.

The activated carbon particles in the activated carbon monolith catalyst10 are dispersed throughout the supporting matrix, giving depth to thecatalyst activity and selectivity. The activated carbon particles arebound by the supporting matrix, which desirably is an inert binder andis not susceptible to attack by reaction media. In the embodiment shownin FIG. 10, the supporting catalyst is a ceramic, but other materialscan be used as the supporting matrix. For example, a mixture ofactivated carbon particles and a polymer resin, such as a thermoplasticpolymer, can be formed into a monolith and pyrolyzed to convert theresin into a carbon matrix.

In one embodiment of the present invention, the activated carbonmonolith catalyst 10 comprises a total catalyst precursor on thefinished activated carbon monolith in an amount from about 0.01 percentto about 5.0 percent by weight of the activated carbon monolithcatalyst. The preferred range depends on the application of the metal ofchoice. For example, with precious metal loading, the total catalystprecursor on the finished extruded activated carbon monolith may be inan amount from about 0.01 percent to about 1.0 percent by weight ofactivated carbon monolith catalyst. In another example, with base metalloading, the total catalyst precursor on the finished extruded activatedcarbon monolith may be in an amount from about 1.0 percent to about 5.0percent by weight of activated carbon monolith catalyst.

The activated carbon monolith catalyst is porous, with pores extendinginto the depths of the monolith walls. Because the activated carbonparticles are substantially discontinuous and are dispersed throughoutthe ceramic matrix, it is possible, depending on the catalyst precursorand the conditions under which the catalyst precursor is applied to themonolith, for the catalyst precursor to be present on the exteriorsurface of the monolith walls, and into the depths of the monolith wallsvia passageways between the discontinuous activated carbon particles,via passageways between the ceramic matrix and the carbon particles, andvia pores in the carbon particles themselves. Placement of the catalystprecursor within the monolith structure can be controlled by selectionof catalyst precursor, and variation in parameters of catalyst precursorapplication such as temperature, ionic strength of catalyst precursorsolution, duration of catalyst precursor application, pH of the catalystprecursor solution, and the like. The catalyst precursor therefor isdesirably disposed on the surface of the finished self-supportingactivated carbon monolith, such surface including area on the exteriorwalls of the monolith as well as area within passageways and pores inthe depth of the monolith walls.

As will be discussed in more detail below, the activated carbon monolithcatalyst 10 is useful in a variety of chemical processes FIG. 2illustrates the flow of fluid through the passages 12 in the activatedcarbon monolith catalyst 10. A catalyst precursor applied on and withinthe walls of the monolith structure, becomes catalytically active, andcatalyzes a chemical reaction as reactants flow through the monolith.

Method of Making the Activated Carbon Monolith Catalyst

Generally described, the activated carbon monolith catalyst 10 is madeby providing a finished self-supporting activated carbon monolith andapplying at least one catalyst precursor to the finished activatedcarbon monolith. According to a preferred embodiment, the finishedactivated carbon monolith is formed by mixing together activated carbon,ceramic forming material, flux material, and water to make an extrudablemixture, wherein binder is optionally added. The extrudable mixture isextruded through an extrusion die to form the monolith having ahoneycomb structure. It is appreciated that the finished extrudedactivated carbon monolith may be a honeycombed structure, or any otherstructure which is capable of being made by the extrusion process. Afterextrusion, the extruded honeycomb monolith retains its shape while it isdried and then fired at a temperature and for a time period sufficientto react or fuse the ceramic forming material together and form aceramic matrix, having activated carbon particles dispersed throughoutthe ceramic matrix or structure, and exhibiting sufficient strength forits intended end use. At least one catalyst precursor is thereafterapplied to the finished extruded activated carbon monolith.

Alternatively to extruding an extrudable mixture to form a finishedself-supporting activated carbon monolith, such monoliths can be formedby pressing a suitable activated carbon and binder mixture with a die orpress, or by drawing a suitable mixture through a die with a suitabledrawing force. For example, a mixture of activated carbon particles anda polymer resin, such as a thermoplastic polymer, can be pressed ordrawn to form a monolith and pyrolyzed to convert the resin into acarbon matrix.

The application of catalyst precursor to the finished activated carbonmonolith may be achieved according to any method known to those ofordinary skill in the art. In one embodiment of the present invention,the finished activated carbon monolith is contacted with a solutioncomprising at least one catalyst precursor, such as for example, apalladium chloride solution. The solution comprising at least onecatalyst precursor, hereinafter is referred to as “catalyst precursorsolution”, is contacted with the finished activated carbon monolith at acontrolled or timed rate. “Controlled” or “timed rate” refers to theaddition of the catalyst precursor solution, or other components of thecoating process, at a defined rate which achieves the desired contact ofthe catalyst precursor to the finished activated carbon monolith.“Defined rate” refers to any rate which is capable of being reproducedor recorded. For example, the “controlled” or “timed rate” may bedefined as a rate of catalyst precursor solution or other coatingcomponent addition at about 0.5 cc/second/gram of finished activatedcarbon monolith to about 50 cc/second/gram of finished activated carbonmonolith. In another example, the timed rate may be 0.5 cc/minute/gramof finished activated carbon monolith to about 100 cc/minute/gram offinished activated carbon monolith.

It is appreciated that one of ordinary skill in the art may vary thetime or volume increments of the addition of the catalyst precursorsolution to achieved the desired catalyst precursor application process.For example, the catalyst precursor solution may be added to thefinished activated carbon monolith at a timed rate of 15.0 cc every 6.0seconds for a 6.0 gram finished activated carbon monolith. The catalystprecursor solution is added for a period of time which will achieve anactivated carbon monolith catalyst comprising a total weight of thecatalyst precursor in the amount of about 0.01% to about 5.0% by weightto the total weight of the activated carbon monolith catalyst. It isappreciated that the time period will depend on the concentration of thecatalyst precursor solution, and the controlled rate of addition of thecatalyst precursor solution. For example, the addition of the catalystprecursor solution may last from about 10.0 minutes to about 1.0 hour.

In a sub-embodiment of the present invention, the catalyst precursorapplication process also comprises other components such as water,buffering agent, optional reducing agent, and optional hydrogenperoxide, optional base, and optional acid. The water preferably isdeionized. As used herein “buffering agent” refers to any compound whichresists changes in pH upon the addition of small amounts of either acidor base. A buffering agent comprises a weak acid or base and its salt.Non-limiting examples of a buffering agent include, but are not limitedto, sodium carbonate, potassium carbonate, sodium hydroxide, potassiumhydroxide, and sodium bicarbonate. As used herein, “reducing agent”refers any substance that can donate electrons to another substance ordecrease the oxidation numbers in another substance. Non-limitingexamples of reducing agent include, but are not limited to, sodiumformate, potassium formate, hydrogen, sodium borohydride, sodiumhypophosphite, hydrazine, and hydrazine hydrochloride. It is appreciateto those of ordinary skill in the art that not all metals such as basemetals require a reducing agent.

In yet another sub embodiment, the chlorides of some metals, usuallybase metals, are soluble alone in water. Others, such as platinum orpalladium, require hydrochloric acid, or being pan of a potassium orsodium chloride compound for improved solubility. For example, palladiumchloride may be dissolved in hydrochloric acid. In another example,sodium chloropalladite is formed by adding sodium hydroxide to palladiumchloride dissolved in hydrochloric acid. Other chemical combinations toimprove the solubility of the catalyst precursor are known in the art.

The temperature of the catalyst precursor solution may be from about30.0° C. to about 75.0° C. In another example, the temperature may befrom about 50.0° C. to about 65.0° C. Preferably the temperature is at65.0° C.

The catalyst precursor solution is usually acidic. For example, the pHof the catalyst precursor solution may range from about 1.0 to about6.9. In another example, the pH of the catalyst precursor solution mayrange from about 4.0 to about 6.5. The catalyst precursor applicationprocess may be carried out in an environment wherein the pH may rangefrom about 1.0 to about 13.0 depending on the equipment and reagentsutilized. It is appreciated that equipment such as stainless steelequipment (i.e. acid reactive equipment) requires a coating processenvironment wherein the pH is basic to avoid deterioration of theequipment. Alternatively, glass or glass-lined equipment may be suitablewhen using an acidic environment for the catalyst precursor application.

In another embodiment, the method for making the activated carbonmonolith catalyst 10 includes first mixing the dry ingredients of theextrudable mixture and then adding the liquid ingredients to the drymixture; however, the order in which the ingredients are added to theextrudable mixture can be varied by alternating mixing of dry and liquidingredients as long as the proper amount of moisture is added to make anextrudable mixture which holds its shape during and after extrusion. Asuitable finished activated carbon monolith is disclosed in U.S. Pat.No. 5,914,294, the disclosure of which is expressly incorporated hereinby reference.

The activated carbon is desirably present in the extrudable mixture inan amount from about 20 to about 70 parts, by weight, and moredesirably, in an amount from about 30 to about 50 parts, by weight. Avariety of activated carbons can be used in this invention. Theactivated carbon surfaces adsorb volatile organic compounds and otherchemical agents. The most suitable activated carbon will depend on theintended application, particularly the nature of the material to beadsorbed. Thus, the physical properties of the activated carbon, such asthe surface area and the pore structure, may be varied depending on theintended application. Desirably, the activated carbon has a nitrogenB.E.T. surface from about 600 to about 2000 m²/g. More desirably, theactivated carbon has a nitrogen B.E.T. surface from about 800 to about1800 m²/g, and even more desirably has a nitrogen B.E.T. surface fromabout 1000 to about 1600 m²/g. Suitable activated carbon can also becharacterized by having a particle size such that more than 40% byweight of the activated carbon passes through a 200 mesh screen, andmore desirably, by having a particle size such that more than 65% byweight of the activated carbon passes through a 200 mesh screen.

Activated carbon suitable for use in the present invention may be madefrom a variety of precursors including bituminous coal, lignite, peat,synthetic polymers, petroleum pitch, petroleum coke, coal tar pitch, andlignocellulosic materials. Suitable lignocellulosic materials includewood, wood dust, wood flour, sawdust, coconut shell, fruit pits, nutshell, and fruit stones. Suitable commercially available activatedcarbons include Nuchar® activated carbon available from WestvacoCorporation of New York, N.Y., Acticarbone® carbon available from CecaSA of Paris, France, and Darco® carbon and Norit® carbon available fromNorit-Americas of Marshall, Tex.

The ceramic forming material is present in the extrudable mixture in anamount from about 20 to about 60 parts, by weight and more desirably, inan amount from about 30 to about 50 parts, by weight. The term ceramicforming material means alumina/silicate-based material which, uponfiring, is capable of reacting together with other ingredients to form ahigh strength, crystal/glass mixed-phase ceramic matrix. In thisapplication, the reacted ceramic material provides a matrix forsupporting the activated carbon, and has sufficient strength towithstand handling and use of the monolith in the intended applicationand maintain its intended shape without cracking or otherwisedisintegrating. The ceramic forming material desirably includes asubstantial portion of moldable material which is plastic in nature andthus, when mixed with liquid, can be molded or extruded into a shape andwill maintain that shape through drying and firing. Such a suitableplastic or moldable material is ball clay. A particularly suitablecommercially available ball clay is OLD MINE #4 ball clay available fromKentucky-Tennessee Clay Company of Mayfield, Ky. Other suitableplastic-like ceramic forming materials include, but are not limited to,plastic kaolins, smectite clay minerals, bentonite, and combinationsthereof. Bentonite and smectites are desirably used in combination withball clay or kaolin.

The ceramic forming material also desirably includes a filler materialwhich is non-plastic and reduces shrinkage of the monolith during thesteps of drying and firing. A non-limiting example of a suitable ceramicfiller is calcined kaolin clay. A particularly suitable commerciallyavailable calcined kaolin clay is GiComax LL available from GeorgiaKaolin Company, Inc. of Union, N.J. The filler desirably is present inthe extrudable mixture in an amount up to about 15 parts, by weight, andmore desirably, from about 1 to about 15 parts, by weight, and even moredesirably, from about 3 to about 10 parts, by weight. Other suitablefiller materials include, but are not limited to, calcined kyanite,mullite, cordierite, clay grog, silica, alumina, and other calcined ornon-plastic refractory ceramic materials and combinations thereof.

The flux material is present in the extrudable mixture in an amount fromabout 4 to about 20 parts, by weight, and aids in forming the ceramicbond between the ceramic forming materials by causing the ceramicforming material particles to react together and form a ceramic matrixat a lower firing temperature than if the flux material were notpresent. More desirably, the flux material is present in the extrudablemixture in an amount from about 4 to about 10 parts, by weight. Suitableflux materials include, but are not limited to, feldspathic materials,particularly nepheline syenite and feldspar, spodumene, soda, potash,sodium silicate, glass frits, other ceramic fluxes, and combinationsthereof. A particularly desirable commercially available flux materialis MINEX®7 nepheline syenite available from Unimin Specialty Materials,Inc. of Elco, Ill.

The binder is present in the extruded mixture in an amount from about0.5 to about 9 percent, by weight, based on the solids content of thebinder, and enhances the strength of the monolith after extrusion sothat the extruded monolith maintains its shape and integrity afterextrusion and through drying and firing. The binder is desirably presentin the extruded mixture in an amount from about 2 to about 7 percent, byweight, based on the solids content of the binder. A particularlysuitable binder is methylcellulose, and a suitable commerciallyavailable methylcellulose is METHOCEL A4M methylcellulose available fromDow Chemical Company of Midland, Mich. Desirably, methylcellulose ispresent in the extrudable mixture in an amount from about 0.5 to about 9parts, by weight, of the extrudable mixture, and more desirably, fromabout 2 to about 7 parts, by weight. Another suitable binder, used incombination with methylcellulose, is an acrylic binder. Examples of suchpolymers are JONREZ D-2106 and JONREZ D-2104 available from WestvacoCorporation of New York, N.Y., and Duramax acrylic binder which isavailable from Rohm & Haas of Montgomeryville, Pa. The acrylic polymer,having a medium to high glass transition temperature is desirablypresent in an amount from zero up to about 4 parts, by weight, of theextrudable mixture, based on the solids content of the acrylic binder.Other suitable binders include hydroxypropyl methylcellulose polymers,CMC, polyvinyl alcohol, and other temporary binder/plasticizeradditives.

Another desirable component of the extrudable mixture is sodiumsilicate, which increases the strength of both the dry, but unfiredmonolith and the fired monolith, and is a flux material. The sodiumsilicate is thus both a binder when the monolith is in the dry state anda flux material, and is added to the extrudable mixture as a solution.The sodium silicate is desirably present in the extrudable mixture in anamount up to about 7 parts, by weight, based on the solids content ofthe sodium silicate, and more desirably in an amount from about 0.0 toabout 7 parts, by weight, based on the solids content of the sodiumsilicate. A suitable commercially available sodium silicate solution isa 40% solids, Type N solution, available from PQ Corporation, IndustrialChemicals Division, Valley Forge, Pa. Other suitable binders for thedried monolith include silica sol and alumina sol.

The extrudable mixture includes water in an amount sufficient to make anextrudable mixture and desirably includes from about 60 to about 130parts water, by weight of dry ingredients. Preferably, the water ischilled before it is added to the mixture and more preferably is addedto the system at or near 0° C. This low temperature helps keep theingredients cool during mixing, and helps to overcome any exotherm whichmay occur as a result of mixing the ingredients, or as a result ofheating of the mixture, which occurs as a result of the mechanicalaction of mixing.

The extrudable mixture is formed into a shape, which will be the shapeof the finished self-supporting activated carbon monolith, by passingthe extrudable mixture through an extrusion die. The finishedself-supporting activated carbon monolith usually has a block orcylindrical shape, and includes at least one passageway along its lengthand desirably includes a plurality of passageways extending along thelength of the finished self-supporting activated carbon monolith. Theactivated carbon monolith catalyst is designed to be placed in a streamof a fluid containing one or more chemical reactants, such that thefluid is forced through the passages in the monolith. Ideally, theamount of internal surface area of the activated carbon monolithcatalyst exposed to the fluid is designed to maximize the efficiency ofthe catalytic reaction. A honeycomb-shaped structure is preferred forthe finished self-supporting activated carbon monolith. Honeycombextruders are known in the art of ceramics and have been used to produceceramic monoliths.

Desirably, the honeycomb structure of the finished self-supportingactivated carbon monolith has an open frontal area greater than 50percent and up to about 85 percent, and desirably about 74 percent,after drying and firing. The open frontal area of the monolith is thepercentage of open area of the monolith taken across a planesubstantially perpendicular to the passageway length of the monolith.Furthermore, the finished self-supporting activated carbon monolithdesirably has a honeycomb pattern with square cells and about 540 cellsper square inch. The honeycomb structure desirably has a cell-to-cellpitch of about 0.043 inches, a cell wall thickness of about 6 mils, andan open frontal area of about 0.0014 square inches per cell. Morebroadly, for a variety of applications, the cell density may vary from 1to 900 cells per square inch or higher, with the cell wall thicknessranging from about 150 mils to about 4 mils, and the cell-to-cell pitchvarying from about 1 to about 0.033 inches.

The extruded activated carbon honeycomb monolith is dried in a manner soas to prevent cracking of the structure. To alleviate cracking, theextruded carbon honeycomb monolith is dried so that water is removed atsubstantially the same rate throughout the carbon honeycomb monolith.Suitable drying methods include dielectric drying, microwave drying,warm air drying with the monolith wrapped in plastic or wet cloths,vacuum drying, freeze drying, and humidity control drying.

After drying, the dried extruded activated carbon honeycomb monolith isfired at a temperature from about 1600 to about 1950° F. and desirablyfrom about 1850 to about 1950° F., in a nitrogen or other non-oxidizingor slightly reducing atmosphere. The activated carbon honeycomb monolithshould be fired at a temperature sufficient to react the ceramic formingmaterials together to create a matrix for holding the activated carbonand maintaining the honeycomb shape of the extrusion. The bonds createdby the firing should be sufficient to create a matrix having a strengthable to withstand handling and use of the carbon monolith catalyst inintended applications. The relatively high surface area of the materialforming the finished self-supporting activated carbon monolith makes itdesirable as a catalyst support. As explained above, the finishedself-supporting activated carbon monolith is porous, and catalystprecursor can be applied on the exterior of the monolith and through thedepth of the monolith via pores and passages in the monolith walls.

In a desired embodiment, the finished self-supporting activated carbonmonolith is made by extruding a mixture comprising: 30 parts, by weight,activated carbon; 50 parts, by weight, ball clay; 10 parts, by weight,calcined kaolin clay; 10 parts, by weight, nepheline syenite; 2.5 parts,by weight, methylcellulose; 2.8 parts, by weight, sodium silicatesolids; and 75 parts, by weight, water. The resulting finishedself-supporting activated carbon monolith has a high structuralintegrity, exhibiting axial crushing strength of about 1500 psi and amodulus of rupture (MOR) of about 150 psi in the axial direction.

It should be understood that the activated carbon monolith catalyst ofthis invention could be used in a variety of applications owing to thewide range of carbon content which the carbon monolith catalysts cancontain. For example, crushing strengths of the finished self-supportingactivated carbon monolith will vary depending on the relative amounts ofcarbon and ceramic forming material, the firing temperature, and theparticle size of the ingredients. In particular embodiments, thefinished self-supporting activated carbon monolith may include activatedcarbon particles in an amount from about 20 to about 95% by weight ofthe finished self-supporting activated carbon monolith, preferably in anamount from about 20 to about 80% by weight of the finishedself-supporting activated carbon monolith, and more preferably in anamount from about 30 to about 50% by weight of the finishedself-supporting activated carbon monolith. The higher loading of carbon(greater then 80% by weight) is more effectively achieved with anon-ceramic matrix such as carbon. The axial crushing strength of thefinished self-supporting activated carbon monolith desirably ranges from500 to 1600 psi.

Catalytic Reactions

In another embodiment of the present invention, a method for catalyticchemical reaction is provided comprising contacting at least onereactant with an activated carbon monolith catalyst comprising (a) afinished self-supporting activated carbon monolith having at least onepassage therethrough, and comprising a supporting matrix andsubstantially discontinuous activated carbon particles dispersedthroughout the supporting matrix, and (b) at least one catalystprecursor on the finished activated carbon monolith.

The term “reactant” as used herein refers to any chemical compound inwhich a catalyst can affect a chemical reaction by increasing thereaction rate, and/or lowering the activation energy, and/or create atransition state of lower energy when the chemical compound is alone, incombination with another chemical compound. or in combination with atleast two chemical compounds of the same species.

The carbon monolith catalyst of the present invention is suitable forvarious catalytic reactions. “Catalytic reaction” or “reaction” as usedherein refers to heterogeneous and homogeneous catalytic reaction.

Heterogeneous catalytic reaction involves the use of a catalyst in adifferent phase from the reactants. Typical examples involve a solidcatalyst with the reactants as either liquids or gases, wherein one ormore of the reactants is adsorbed onto the surface of the catalyst atactive sites. Homogeneous catalytic reaction, on the other hand,involves the use of a catalyst in the same phase as the reactants.

In one embodiment, nitrobenzene is passed through the activated carbonmonolith catalyst comprising palladium, and under hydrogen pressure. Theresult is the production of aniline.

In another embodiment, phenol is passed through the activated carbonmonolith catalyst comprising palladium doped with sodium, and underhydrogen pressure. The result is the production of cyclohexanone.

In yet another embodiment, crude terephthalic acid containing such colorbodies as 4-carboxybenzaldehyde is passed through the activated carbonmonolith catalyst comprising palladium, and under hydrogen pressure. Theresult is the production of purified terephthalic acid with very fewcolor bodies present.

In yet a further embodiment, hydrogen and nitrogen are passed throughthe activated carbon monolith catalyst comprising ruthenium, and underpressure and heat. The result is the production of ammonia.

In another embodiment, carbon monoxide or carbon dioxide is passedthrough the activated carbon monolith catalyst comprising ruthenium, andunder hydrogen pressure and heat. The result is a hydrocarbon,Fisher-Tropsch Synthesis.

In yet another embodiment, hydrocarbon and water are passed through theactivated carbon monolith catalyst comprising ruthenium. This process isalso known as steam cracking. The result is hydrogen and carbonmonoxide, wherein the hydrogen may be used in a fuel cell.

In yet another embodiment, Nitrobenzene is passed through the activatedcarbon monolith catalyst comprising platinum, and under hydrogenpressure. The result is the production of aniline.

In another embodiment, hydrogen and oxygen are passed through theactivated carbon monolith catalyst comprising platinum, in a fuel cell.The result is electricity.

In another embodiment, amine and aldehyde or ketone are passed throughthe activated carbon monolith catalyst comprising sulfided platinum, andunder hydrogen pressure. The result is a reductive alkylation product.

In another embodiment, nitrobenzene is passed through the activatedcarbon monolith catalyst comprising sulfided platinum, and underhydrogen pressure. The result is a hydroxyl amine.

In another embodiment, aniline is passed through the activated carbonmonolith catalyst comprising rhodium, and under hydrogen pressure. Theresult is the cyclohexylamine.

In another embodiment, phenol is passed through the activated carbonmonolith catalyst comprising rhodium and under hydrogen pressure. Theresult is cyclohexanol.

In another embodiment, gas phase catalytic reaction may also be achievedwith the activated carbon monolith catalyst of the present invention.Non-limiting examples include:

Cyclic-Condensation and Dehydrogenation, Heterocyclic CompoundsSynthesis

wherein R represent any chemical functional group which does not alterthe chemical compounds.

Other reactions in which the activated carbon monolith catalyst mayparticipate includes, but are not limited to, chlorination,isomerization, heterobicyclic compounds synthesis, polymerization,hydrodesulfurization, and hydrodenitrogenation.

It is appreciated that one of ordinary skilled in the art, presentedwith the teaching of the present invention, may arrive at all theavailable permeations of reactants and catalytic reaction reactions.

The present invention is described above and further illustrated belowby way examples which are not to be construed in any way as imposinglimitations upon the scope of the invention. On the contrary, it is tobe clearly understood that resort may be had to various otherembodiments, modifications, and equivalents thereof which, after readingthe description herein, may suggestion themselves to those skilled inthe art without departing from the scope of the invention and theappended claims.

Example 1

Approximately 2 L of de-ionized water was added to a 3 L heated glassreactor, and agitated by a variable speed motor attached to a plasticimpeller. The temperature was ambient, and recorded via a thermocoupleconnected to a recording device. A quantity of sodium carbonate wasadded to the water in the stirring reactor so as to elevate the pH toabout 10.5.

A finished self-supporting activated carbon monolith made in accordancewith U.S. Pat. No. 5,914,294 was placed in the reactor so as to have thesodium carbonate aqueous solution pass evenly through the cells of themonolith as the solution was agitated.

In another glass container, a solution of palladium chloride wasprepared so as to have a palladium. metal loading by weight of thecarbon monolith of 0.1%. The pH of this solution was adjusted to a pH of4.0 using sodium bicarbonate. This solution was metered into thereactor.

After the metering of the palladium solution, the reactor was heated viaan electronic temperature controlled device, so as to ramp to 65° C. in30 minutes.

After the temperature of the reactor had stabilized at 65° C., asolution of sodium formate in water was metered into the reactor, andthe reactor was allowed to stir for an additional 30 minutes.

Power to the heater was turned off and the reactor was allowed to coolto below 40° C., after which agitation was stopped, and the activatedcarbon monolith catalyst removed and washed free of any minerals, suchas chlorides, by the use of de-ionized water.

Example 2

In the same manner of Example 1, a finished self-supporting activatedcarbon monolith made in accordance with U.S. Pat. No. 5,914,294 was usedto prepare a catalyst with a palladium metal loading of 5% by weight ofthe activated carbon monolith catalyst.

Ingredients were increased proportionally to the amount of palladiummetal used in this Example 2, as compared to Example 1.

Example 3

The activated carbon monolith catalyst of Example 2 was tested for itscatalytic activity using nitrobenzene as a test reactant.

The activated carbon monolith catalyst was placed in the 500 ml glassbottle of a Rocking Parr Bomb. A quantity of 2 ml of pure nitrobenzenewas added to the glass bottle along with 50 ml of methanol to act as asolvent. The bottle was inserted into the Rocking Parr Bomb at ambienttemperature, which was 22° C. at the time of the test.

The bottle was pressurized to 60 psig with pure hydrogen. When agitationof the bottle commenced, time and hydrogen pressure in the bottle wererecorded. Hydrogen pressure was seen to fall from 60 psig to 43.5 psigin 255 seconds. The temperature of the contents of the bottle were seento rise from 22° C. to 31° C. in the same time period. These are directindications of a catalytic reaction occurring with the nitrobenzene andhydrogen due to the presence of the activated carbon monolith catalystin the bottle.

Further assurances of the reaction were test runs with no activatedcarbon monolith catalyst present in the test bottle containing thenitrobenzene and methanol solution as described above, where notemperature increase or drop in hydrogen pressure from 60 psig wasobserved, and another run with palladium sponge replacing the carbonmonolith catalyst, where a very slight drop in hydrogen pressure wasobserved, but no appreciable temperature change was observed.

While the invention has been described in detail with respect tospecific embodiments thereof it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereof.

1. A method for catalytic chemical reaction comprising contacting at least one reactant with an activated carbon monolith catalyst comprising (a) a porous finished self-supporting activated carbon monolith having walls defining at least one passage therethrough and comprising a supporting ceramic matrix and substantially discontinuous activated carbon particles dispersed throughout the supporting ceramic matrix, the walls having an exterior surface, depth, and passageways into the depth of the walls, and (b) at least one catalyst precursor on said porous finished self-supporting activated carbon monolith, the at least one catalyst precursor applied to the porous finished self-supporting activated carbon monolith and disposed on the exterior surface of the walls and within the passageways into the depth of the monolith walls of the porous finished self-supporting activated carbon monolith.
 2. A method as in claim 1, wherein the at least one catalyst precursor is selected from the group consisting of reduced precious metal, precious metal oxide, precious metal sulfide, precious metal with modifier, base metal, or a combination thereof.
 3. A method as in claim 1, wherein the at least one catalyst precursor includes a modifier selected from the group consisting of potassium, calcium, magnesium, sodium hydrated oxides, and sodium hydroxides.
 4. A method as in claim 1, wherein the at least one catalyst precursor is a precious metal selected from the group consisting of palladium, platinum, rhodium, ruthenium, iridium, osmium, silver, and gold.
 5. A method as in claim 1, wherein the at least one catalyst precursor is a base metal is selected from the group consisting of zinc, nickel, copper, manganese, iron, chromium, vanadium, and molybdenum.
 6. A method as in claim 1, wherein the at least one catalyst precursor is a base metal catalyst selected from the group consisting of oxides, hydrated oxides, carbonates, or sulfides.
 7. A method as in claim 1, wherein the at least one catalyst precursor is present on the finished self-supporting activated carbon monolith in an amount from about 0.01% to about 5.0% by weight of the activated carbon monolith catalyst.
 8. A method as in claim 1, wherein the finished self-supporting activated carbon monolith has an axial crushing strength from about 500 to about 1600 psi.
 9. A method as in claim 1, wherein the activated carbon particles are present in the finished self-supporting activated carbon monolith in an amount from about 20 to about 95% by weight of the monolith and the supporting matrix is present in the finished self-supporting activated carbon monolith in an amount from about 80 to about 5% by weight of the finished self-supporting activated carbon monolith.
 10. A method as in claim 1, wherein the activated carbon particles are characterized by a nitrogen B.E.T. surface area from about 600 to about 2000 m²¹ g.
 11. A method as in claim 1, wherein the activated carbon particles are characterized by having a particle size such that more than 40% by weight of the activated carbon passes through a 200 mesh screen.
 12. A method as in claim 1, wherein the finished self-supporting activated carbon monolith is made according to a process comprising extruding an extrudable mixture comprising the activated carbon particles, ceramic forming material, flux material and water, drying the extruded monolith, and firing the dried monolith at a temperature and for a time period sufficient to fuse the ceramic forming material together and form the ceramic matrix.
 13. A method as in claim 12, wherein the flux material is a feldspathic mineral.
 14. A method as in claim 13, wherein the feldspathic mineral is nepheline syenite.
 15. A method as in claim 12, wherein the flux material further comprises sodium silicate.
 16. A method as in claim 12, wherein the ceramic forming material is selected from the group consisting of ball clay, plastic kaolins, smectite clay minerals, bentonite, and combinations thereof.
 17. A method as in claim 12, wherein the ceramic forming material further comprises a shrinkage reducing filler material.
 18. A method as in claim 1, wherein the finished self-supporting activated carbon monolith further has a plurality of passages therethrough for receiving a flow of fluid and an open frontal area greater than 50% and up to 85%.
 19. A method as in claim 1, wherein the finished self-supporting activated carbon monolith is honeycomb shaped.
 20. A method as in claim 1, wherein activated carbon particles have pores and the at least one catalyst precursor is at least partially disposed in pores of the activated carbon. 